1. Field of the Invention
The present invention relates to a disposable diaper which fits the body of a wearer, more particularly to a disposable diaper which can prevent the positional shift of a protector against incontinence and the side leaking of urine when the protector is used.
2. Prior Art
A disposable diaper comprises a back sheet, a top sheet and an absorbent core interposed between the back and top sheets. The back sheet is made of a liquid non-permeable but finely air permeable resin sheet so as to prevent the outside oozing of urine. Furthermore, the top sheet to face the skin of a wearer is made of a material gentle to the skin, such as non-woven fabric or soft porous sheet, both liquid permeable, so that fluids such as urine permeates through the top sheet into the absorbent core. As the absorbent core, additionally, use is made of crushed pulp or a mixture of crushed pulp and super absorbent polymer.
In order to fit the body outline of a wearer, the absorbent core is produced by cutting into a sandglass-like form. After cutting, the absorbent core is interposed between the back sheet and the top sheet. The back sheet and the top sheet both are of a shape similar to the shape of the absorbent core but with a larger outline than the absorbent core. At both ends thereof where no absorbent core is present, these back sheet and top sheet are bonded together by means of a hot-melt adhesive.
A back waist region of disposable diaper is attached to the dorsal area of a wearer; a crotch region thereof is attached to the crotch thereof; and a front waist region thereof is attached to the abdominal area thereof. By drawing forward flaps of the back waist region which flaps elongate in the width direction of the diaper to overlay the flaps over the front waist region, the front waist region and the flaps are fastened together. Thus, the diaper is completely worn.
Generally, flat elastic braids capable of elongating toward the longitudinal direction (lengthwise direction) of the diaper are partially bonded, at their elongated state between the back sheet and the top sheet, to both sides of the crotch region in the crosswise direction (width direction) by means of a hot-melt adhesive, thereby forming gatherings to be applied to the thigh parts of a wearer.
A disposable diaper for adults is far larger than a disposable diaper for infants and toddlers, requiring a larger volume of raw materials for one diaper piece and thus costing high per unit price. Therefore, it is not economical to change the diaper for adults to new one in each time of excretion of urine. Accordingly, a protector against incontinence is generally used in combination with the diaper. After urine excretion, then, only the protector against incontinence is changed.
Such a protector against incontinence is formed of a lamination body in a sheet-like form, comprising an outer sheet comprising for example a liquid non-permeable resin sheet, an inner sheet comprising for example a non-woven fabric, and an absorbent core interposed between the outer and inner sheets. At ends in the lamination body in the width direction and the longitudinal direction where no absorbent core is present, the outer sheet and the inner sheet are bonded together by means of a hot-melt adhesive. To the ends in the width direction, additionally, elastic members such as flat elastic braids are partially bonded at its elongated state between the outer sheet and the inner sheet. The elastic member forms a gathering.
The lamination body in the sheet-like form is preliminarily deformed in the shape of a cone so that the center of the lamination body in the longitudinal direction forms the peak of the cone when the protector against incontinence is worn. Through an adhesive part provided to the lamination body, both ends of the lamination body are bonded together.
The disposable diaper should be used in such a manner that when a male wearer wears the protector against incontinence, the protector adheres to the top sheet of the diaper in the crotch region thereof by another adhesive part provided to the protector to prevent the shift of the protector in the diaper.
The same protector may be used for females. In this case, the protector is applied to the diaper such that, while the longitudinal direction of the lamination body should be aligned along the longitudinal direction of the diaper, the outer sheet of the protector should face the top sheet of the diaper to overlay the protector over the crotch region of the diaper. Then, the adhesive part of the protector adheres to the top sheet of the diaper to prevent the shift of the protector on the diaper. In such manner, the protector is used.
As described above, the diaper is in a sandglass-like form, wherein the width of the crotch region is narrower than the widths of the front waist region and the back waist region. Because urine is mainly absorbed in the crotch region, however, the crotch region should be wide enough to absorb urine. Therefore, the crotch region is generally formed at a larger width than the width of the crotch of a wearer.
Therefore, in the case when such a diaper is worn, the crotch region expands in a bag-like shape because the crotch region is pressed by the thigh parts of a wearer from both sides in the width direction, so that a space is formed between the crotch of the wearer and the diaper. When the diaper is used in combination with a protector against incontinence, therefore, the protector is positioned in the front side of the expanded crotch region of the diaper. Then, the protector is not pressed sufficiently against the body. When the wearer makes a motion, therefore, the protector so readily makes a positional shift in the diaper that the protector cannot effectively absorb urine.
In a border region between the front waist region and the crotch region of the diaper, in particular, the individual dimensions of these regions in the width direction are prominently different from each other. When the crotch region is pressed by the thigh parts of a wearer, therefore, the border region is apt to expand more on the side closer to the front waist region, and the protector for males is mounted on this side of the border region. When the front waist region side of the border region expands as has been described above, therefore, the force of the diaper to press the protector is weakened especially for males, to readily cause the positional sift of the protector.
Furthermore, when the diaper is directly worn without any protector against incontinence, excretion such as urine and feces readily leaks from the front waist region side of the border region.
When the direction from the front waist region through the crotch region to the back waist region is defined as the longitudinal direction of the diaper, conventionally, the pitch of the front retaining fasteners arranged on the front waist region in the longitudinal direction has been almost the same as the pitch of the back retaining fasteners arranged on the flaps of the back waist region in the longitudinal direction. When the flaps of the back waist region are overlaid over the surface of the front waist region to fasten the front and back retaining fasteners together, therefore, the diaper forms a cylindrical shape at a portion to be applied to the wearer's hips and waist. The dimension of the inner diameter (diameter size) of the cylinder is kept at almost the same value all through the longitudinal direction of the cylinder.
However, the outer size of the waist (waist size) of humans is generally smaller than the outer size of the hips (hip size) thereof. Therefore, in the diaper with the front and back retaining fasteners fastened together, the inner size of the cylinder is adjusted to the outer size of the hips, so that some space is formed between the diaper and the wearer's waist. When the front and back retaining fasteners are fastened together, therefore, the diaper cannot fit the waist, causing insufficient fastening of the diaper around the waist, which possibly causes certain positional shift of the diaper. Compared with infants and toddlers, adult body shape has such a larger difference in outer size between the hips and the waist that the diaper can hardly be fastened sufficiently around the waist.
Even in the diaper for new born babies or infants, furthermore, since the absorption core in the crotch region is more voluminous, the expansion of the diaper in the crotch region is increased when the diaper is worn. If the diaper has a cylindrical shape with a uniform inner size, therefore, it is very difficult to fasten sufficiently the diaper around the waist of the wearer or the abdomen thereof.
It is an object of the present invention to provide a disposable diaper wherein a border region between a front waist region and a crotch region is prevented from expanding toward the direction free from the body of a wearer.
It is another object of the present invention to provide a disposable diaper which is securely fastened around the waist of a wearer.